1. Field of the Invention
This invention relates to a tide gate check valve for large-sized conduits, particularly storm sewer pipes having diameters on the order of at least about 36 inches.
2. Description of the Prior Art
A check valve is essentially a valve which allows fluid flow in only one direction through a tube, pipe, duct or conduit, while closing and preventing back or reverse flow, when back pressure builds up downstream of the valve to a level greater than the initial fluid pressure head.
Many types of check valves have been proposed in the prior art, especially spring-loaded check valves, in which there are moving parts. In many instances, a substantial pressure differential is required to open and close such types of check valves. Thus, such valves entail a substantial pressure loss in many instances, and such valves may jam in the open position, due to the provision of the usual shafts, pivot pins, bushings or bearings. Pin and bearing fatigue often cause failure in such check valves. The valve seat may leak due to foreign matter or seat obstructions. Noise, slamming or chatter are frequently prevalent with such types of check valves. Sliding, rotating, swinging and plunging parts lead to wear and failure or jamming, especially when handling slurries or other fluids containing entrained particulate solid material. Thus, many types of mechanical check valves of the prior art are subject to leakage, noisy operation, high pressure loss, and stuck open valves. A fail-safe fluid control valve which functions as a check valve is disclosed in U.S. Pat. No. 4,071,038.
One variety of check valve which has been developed in recent years entails a valve body in which there is a flexible resilient check sleeve which terminates with a tapered duck-bill configuration and a rectilinear outlet end which opens to an oval or circular shape to accommodate successively greater fluid flow, but which closes on back pressure build-up. One problem with such valves, especially in larger sizes, is that when a high back pressure is induced, the duck bill sleeve collapses and inverts, thus permitting back flow of fluid.
This problem is especially acute in handling storm sewer effluent to tidal discharge. All cities near waterways use tide gate valves, such a valve being a hinged, wooden, large diameter valve attached to the discharge end of the storm sewer pipe. When there is a storm, storm water from the streets runs into these very large storm sewers and flows either into the ocean or rivers. When the tide is in, these storm sewers back fill with either ocean or river water. This leaves no storage capacity in the sewer. This causes flooding in cities during a heavy downpour, and may actually flood out metropolitan areas. Tide gates were invented over 100 years ago and have not been improved to any substantial degree since then. Trees, logs and bricks get into these gates and jam them. Up to the present, there was no feasible check valve for large sized ducts and conduits of 36", 72", or even greater diameter. A design problem in such cases is inversion, because for a large diameter check valve, the area is quite great, and the even low back pressure multiplied times the area will invert and collapse the flexible sleeve of the duck bill check valves, thus allowing reverse flow of fluid to take place.